This application claims the priority of German Application No. 103 14 688.1 filed on Mar. 27, 2003, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a process for applying double-layered rigidity strips to a sealable foil web, which is transported in sequences, whereby V-shaped loops are formed at predetermined foil sections set at a distance from one another in transport direction, and whereby the sides forming the loops are sealed to one another so that the then formed rigidity strips, extending transversely to the transport direction, project collar-like from the foil web.
From an article in the magazine Packaging Strategies dated Nov. 30, 2002, a new type of packaging pouch with the name EdgeStand is known, which is manufactured from a sealable foil web and which is provided around its entire bottom edge with a rigidity strip. This rigidity strip enables the pouch to stand on an even surface and even to be stacked. The rigidity strip is folded onto the pouch and is double-layered. There is no information provided in the article on the method of production, but the applied process is known to the applicant of the present invention through prior notorious use. The folding of the double-layered rigidity strips onto the foil web hereby occurs along a plane transport path, along which the elements required for carrying out the process are adapted to a predetermined format of the packaging pouch to be made. In the case of products with other formats, in particular in the case of varying distances between the foil sections to be folded, different function elements must be fitted in a complicated process.
It is an object of the present invention to avoid time-consuming retrofitting of the function elements in a process of the type described above.
This object has been achieved in accordance with the present invention in that a controlled auxiliary loop is arranged at each foil section on which a loop is formed, said auxiliary loop serving the adaptation to format changes regarding the distances between the foil sections.
An auxiliary loop of this type can be very easily controlled by means of notch markings arranged at the foil web, for example, or recesses or pressure marks, by means of which format changes can be very quickly carried out. If required, this can take place without interruption, whereby it is even possible in particular cases to process various formats on one and the same foil web. Furthermore, an auxiliary loop of this type ensures an additional fine adjustment in the form of a tolerance based longitudinal compensation, in which short longitudinal fluctuations are immediately and automatically corrected.
The auxiliary loop advantageously is maintained for several stages in the sequence during the transport of the foil web. Thus the overall process is accelerated by means of a shortening of the sequences times, which process is described in more detail below with the aid of description of the drawings. The auxiliary loops are maintained by means of clamping to a transport means, which ensures a reliable fixing thereof. This even permits a plurality of auxiliary loops to be simultaneously maintained, according to the subsequently occuring stages of the process.
Should the process be applied in the case of very variable format changes, the auxiliary loop can be divided into two smaller loops.
The present invention also describes an arrangement for carrying out the process, comprising a folding knife which forms the loops, also comprising two nipping jaw pairs arranged at the folding knife and clamping the foil web directly upstream and directly downstream of a loop, also comprising a pressing device which presses the sides of the loops to one another, also comprising a heating device arranged at the pressing device and also comprising a transport roller arranged at the folding knife, said transport roller being driven in sequences. For an arrangement of this type it is provided in accordance with the present invention that the transport roller is a drum having a relatively large diameter and having devices around its circumference for forming a plurality of loops and auxiliary loops.
A drum of this type permits not only the execution of the process for various formats on the foil web, but it also causes a saving of time in that the circumference of the drum goes past a plurality of control points. In a preferred embodiment of the present invention it is provided that the pressing device comprises for each loop two rotating pressing jaws which are movable in relation to one another and which rotate with the drum, said pressing jaws forming at the same time one nipping jaw for the two nipping jaw pairs, whose other nipping jaw is arranged outside of the drum, but positionable thereto.
The above mentioned positioning of the pressing jaws permits, in a simple way, the created rigidity strip to project out either forwards or backwards in transport direction of the foil web. In order to achieve this, the pressing jaws, at their areas forming the respective nipping jaw, are arranged at varying diameters of the drum. When, for example, as is seen from the description of the drawings below, the first pressing jaw in transport direction has the smaller outer diameter, the rigidity strip then projects, collar-like, forwards. When the reverse is the case, that is, the first nipping jaw in transport direction has the larger outer diameter, the rigidity strip projects, collar-like, backwards.
The application of the above mentioned drum permits all the pressing devices rotating therewith to be arranged at only one joint folding knife, arranged outside of the drum, for forming the loops. In the same way, for all the auxiliary loops there can be arranged only one joint format roller arranged outside of the drum. While there is only one function element for directly forming the loops and the auxiliary loops, there is a plurality of pressing devices for sealing the loops to one another, said pressing devices being distributed around the circumference of the drum.
For the purposes of the invention, a sector, arranged for a plurality of pressing devices and having heating devices, is arranged at the drum. Thus the sealing of the sides of the loops to one another is distributed over a plurality of stations, so that the sequence time for each individual sequence is reduced. This sequence time can be further reduced when a sector with cooling means is arranged downstream of the sector arranged for the heating elements.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying schematic drawings wherein.